A. Field of Invention
The invention relates to stringed instruments, more particularly to devices for changing the tuning of the strings thereon simultaneously.
B. Description of Prior Art
In stringed instruments of the type under consideration, e.g., guitars, ukuleles, banjos, mandolins, and even violins, the pitch to which a string is tuned can be increased by stretching the string and thereby increasing its tension, and the pitch can be decreased by slackening the string and thereby decreasing its tension. The amount of the increase or decrease in tension controls the amount of the change in pitch for a given string under a given amount of initial tension.
Kraft U.S. Pat. No. 3,437,001 discloses a tuning device for a stringed instrument which employs a rockshaft to which the strings are attached, said rockshaft being manually rotatable. The strings are attached to the rockshaft so that they are effectively tangent to a circle centered on the axis of the rockshaft having a radius that can be adjusted for each string. The device is capable of increasing or decreasing the pitch of all the strings simultaneously, and it can be conveniently used to increase or decrease the pitch of all the strings by amounts which will preserve their initial tonal relationship, e.g., to tune all the strings up or down one-half step, etc.
Harlin U.S. Pat. No. 3,404,595 discloses a system of levers (two for each string) for increasing or decreasing the pitch of each string and a cross bar with adjustable screws for operating on all the strings in one motion. Though not specifically discussed, the device appears adapted to leaving the tuning of one or more strings unchanged while changing the tuning of the other strings. The tuning change generally begins at a different time for different strings, and the Harlin lever and cross bar system is designed for operation by a foot treadle.
The following patents, less relevant than Kraft and Harlin, are of some interest: Kauffman U.S. Pat. No. 2,241,911, Turman U.S. Pat. No. 2,949,806, Jeffery U.S. Pat. No. 3,252,368, Watson U.S. Pat. No. 3,382,749.